Tuesday, 9 September 2014

I've been adding lots of buildings in Hull. Tracing from imagery is a bit tedious, but I have got into a rhythm. Adding the house numbers I find easier with a printed map with the buildings already drawn then I can note significant points like house numbers near junctions, any extras (like 4a), any gaps in numbering and whether there is a 13 or not. I was working on Beverley Road. Wanted some shopping so I decided to go shopping there, so I could see the layout of the shops as well as any numbering. I also remembered a couple of developments that were worth looking at to see if they were accessible.

I went to The Jacobs Homes off Askew Avenue. The place was complete, smart
and easy to go round, number one complete. Then I went to The Sidings. This is still only partly complete, with two road names (neither called The Sidings of course, this was a railway goods yard many, many years ago). One small road joined these two named ones - I got its name from a house number with the street name under it. Number two complete. I then set off towards the junction between Beverley Road and Cottingham Road to look at the shops and buy a few things.

Before I got to the shops I saw a yellow board with a development name on it I didn't recognise, Scholars Gate, so I followed it. The development is far from complete but a substantial number of houses have been built and many look occupied. Once again no name board, but once again a house number had the road name on it so I could get the details. Number three complete.

When I got to Cottingham Road shops I took lots of photos of the shop fronts from across the street, got asked what I was doing and handed out a leaflet about OSM. When I'd done my shopping I set off for home.

I noticed another new development off Cottingham Road. When I had turned round and got back to it I realised it was gated and the gate was shut. The sign said Chancellor's Court (private road). As I sat in front of the gate I saw a sensor on a wall inside the gate and guessed that if I could get in, the sensor would open the gates to let me out. Just then a van pulled up near the gates at the otherside and they opened, so I drove in, hoping I was right. I drove down the road, turned at the end and set off out. The gates didn't open. I sat near them waiting for someone else to open the gates and a few seconds later a car pulled past me and the gates opened. I followed the car out and my lock in was over. Number four complete.

As I drove home I saw another yellow board for a development, this time in Cottingham at Cleminson Gardens. I had added bit of the development when it was first accessible. Now the whole road loop is accessible and most of the houses look complete and occupied. That completed number five.

Monday, 1 September 2014

In 2007 large parts of Hull and surrounding areas were flooded. The reasons why are still being debated. Drainage capacity, pumping capacity, pumping failures and poor coordination of various agencies have been blamed in reports.

Most flooding in the UK in the past has been either due to rivers bursting their banks or coastal flooding. Coastal flooding along the east coast is often somewhat predictable as it is often the combination of a spring tide, a deep depression and winds from the north or north west blowing down the North Sea. The low pressure allows the sea level to rise, the wind blows the water into the bottle-neck of the southern North Sea and combined with a spring tide the winds blow waves over sea defences which quickly floods land behind the defences.

Rivers bursting their banks is a bit more obvious. Heavy rainfall runs off land and fills water courses, which may burst their banks downstream and flood surrounding land. What we are beginning to see in Britain are more cases of another kind of flooding: direct flooding from heavy rainfall. Here saturated ground and impermeable ground cannot hold any more rainfall, so water sweeps across the surface of land to a low point where it forms a temporary flood, as it did in Hull in 2007. Britain's existing drainage infrastructure tries to deal with this using ditches and other water courses but they are now unable to cope more and more often.

I think more concentrated, heavier rainfall is causing part of this, some of which is down to climate change no doubt. Some of the flooding is man-made in other ways too. Ditches and other water courses are badly maintained and even being filled in. Building causes more run off from roofs, roads and other impermeable surfaces.

One decision made, I think, in the 1950s is also having a devastating effect and that is where any land run off water goes. In most cases the water boards of the 1950 decided to direct run off into sewers. At the time most areas with access the coast simply dumped untreated sewage into the sea and land run off was seen as a way to dilute it. Now all sewage is supposed to be treated before discharge. I said 'supposed to be treated' because the Water Act allows water companies some discretion to pump untreated sewage into the sea when their infrastructure is overwhelmed in an excessive rainfall event. At Bridlington a new pipe has been built for this purpose.

Adding relatively clean land run off to sewage has two big effects. Land run off water ends up getting treated as sewage in expensive treatment works. This water could reasonably be discharged directly into natural water courses or the sea without much problem, instead sewage works with greatly inflated capacity have to be built and run to deal with it. The second big effect is that when unusually heavy rainfall events overwhelm the drainage system, the bottlenecks are the sewage pipes which overflow, putting not just land run off into streets, gardens and homes but sewage too. Fixing this is not easy and will be very, very expensive and disruptive but as climate change progresses some changes will be needed.

I have been helping Cottingham Flood Action Group to understand the drainage and sewer network for that low-lying village by using their knowledge and surveys to add the ditches, drains, culverts, sewers and manholes to OSM and produce a map to help them understand the issues. You can see the map here. So far only a small part of the sewer network of the village has been added but various people in the group have enough knowledge to add the whole network I think. Then the onward link to Hull's network needs adding, which is a much bigger task. All of the network ends up in a single treatment works at the east of Hull at Salt End.

About Me

Like maps, especially OpenStreetMap. Anything tech and science interests me. I like building stuff and working out how things work. My allotment is a great place to be and feeds us lovely food. I like the countryside and wildlife around me.